In case you’ve been living under a rock, LocalStorage is a JavaScript API that allows you to store content in the browser’s cache and access it later on when you need it. Similar to how cookies work, but you’ve got much more than ~4KB (the maximum size for a cookie). That said, while there’s no size limit for each key/value pair in LocalStorage, you’re restricted to around 5-10 MB for each domain. I say 5-10 MB because as per usual, different browsers have different maximum limits. Classic!

Recently we’ve had the opportunity to use LocalStorage for our content. I quite liked it at first because it was very simple to use, but it wasn’t long before we ran into issues. Get this: LocalStorage stores content indefinitely, while SessionStorage stores content for the lifetime of the browser session… and there’s no middle ground. What if I want to store something for 30 minutes? Tough luck!

To make things more interesting, even though some browsers report that they have LocalStorage (I’m looking at you, Safari in Private Browsing mode!) you can’t actually use it (trying to write to/read from it will throw an exception).

Bearing these in mind, we decided to write a small custom library that gives you the ability to use expiries, fail-safe LocalStorage detection, and callbacks for when fetching data doesn’t run as expected.

This method makes sure we can actually use LocalStorage, bypassing the likes of our aforementioned friend, Safari in Private Browsing mode. Here we wrap the LocalStorage set/get in a try/catch statement to catch any read/write exceptions.

Then, we call supportsLocalStorage() at the start of all the other methods to ensure we can actually use LocalStorage. If not, just abort any call early.

Now let’s look at the setter, setItem():

Not a particularly complex method when you think about it. The first two parameters are the key and value for the content you want to store. If you’re experienced with JavaScript (or any other language that uses the concept of keys and values with arrays/objects/hashes/etc) you’ll understand what they mean with no problems. The value can be anything that the core JSON object can stringify.

The last parameter, expiry, is an optional numeric parameter that if supplied, is used as the lifespan of your key/value combination. When combined with our LocalStorage getter, we can use this expiry value to know whether we should bust the key/value next time we go to fetch it!

Be warned: there’s not a tremendous amount of validation ensuring legitimate numbers are used as an expiry – just provide an integer for the number of seconds you want your key/value combination remaining valid in the LocalStorage cache. It’s easy, you’ll be fine.

You’ll notice this method returns true without checking whether your item was actually set in LocalStorage. Unfortunately the API itself doesn’t return a “save” response, so we have to assume the best and say that it did. But if this isn’t good enough, you can write a fetch method to confirm your suspicions. To me, that seems like overkill because the ideal time to check your item is when you’re actually fetching the data to use it. LocalStorage, like cookies, can be easily modified by the end user, so don’t assume that just because you saved it, it’ll be there the next time you go to pull it.

Our next very important method is our getter, getItem()!

This method is a little more complex. Obviously, the first parameter is the key name for the value you want to retrieve. The second value, however, is a callback you can provide to handle when a value doesn’t exist in LocalStorage. While a callback isn’t technically necessary, because LocalStorage calls aren’t asynchronous, I prefer using them as I feel it makes my code neater.

In your closure, your value in LocalStorage will be returned if it exists. Otherwise, if it doesn’t exist or if it has expired, you’ll get a null return value. This was the cleanest way I could come up with for handling both scenarios, which unfortunately does mean having to do an if/else statement in the closure to check whether the response is null or not.

Finally, our last method is a simple remover method.

The native LocalStorage method doesn’t return a status on whether the operation was successful or not, so I mimic the core method by returning void. Again, you could use a getter to ensure data has been removed, but I don’t really see a point in ensuring the core method has worked correctly.

Usage Examples

Both of these examples use the expiry feature in the LocalStorage helper. If the devices key/value doesn’t exist in LocalStorage, we’ll fetch it via AJAX and save it to LocalStorage for 1 hour (60 minutes), then either pass it off to another function or return it.

And there you have it! Check the Bitbucket snippet link for the latest updates as we continue to use and refine our LocalStorage helper.

When Instagram added the ability to upload non-square media images to their service, the only way to get a cropped version of the image from the API was via the thumbnail attribute from the media endpoint. Those familiar with the API would know that Instagram’s thumbnails are served at a rather small size of 150×150 which is alright in some cases, but if you need a larger thumbnail size a 150×150 image scales up very poorly.

Here’s the images attribute in the API response for a recent Instagram post we did:

And here’s the thumbnail for that image:

Scaling that thumbnail up even 1.5 times makes it look very grainy and shows very little detail. For normal square images you can just use a different image size (like low_resolution or standard_resolution), but for images that aren’t square, you won’t get a nice square image. Not great if you’re trying to use a square grid to display Instagram pictures.

Now, here’s the images attribute in an API response for another recent Instagram post we did, except this time the image in question is landscaped:

Instagram are nice enough to provide a cropped, square version of the image for the thumbnail, but the low_resolution and standard_resolution URLs are both uncropped and are not square. Gross!

Say we want a 320×320 thumbnail of the Instagram post, but as you can see, we want a square image. If we use the low_resolution URI, we’ll get this:

If you take a look at the URIs for the images, you’ll notice that the thumbnail URI has an extra parameter in the filename path… the magical crop dimensions! Unfortunately, the crop dimensions aren’t accessible anywhere else in the API (as far as I know), except for in the thumbnail URI. With a bit of spelunking and messing around with the URI, you can change the s150x150 part of the URI to s200x200 for example to get a 200×200 sized thumbnail.

With that in mind, I’ve set the thumbnail URL to use 320×320 instead of 150×150 and voila! We have a larger, square version of the Instagram image:

Note that you can’t provide arbitrary dimensions and expect the API to automagically generate custom images sizes to your specification (Instagram isn’t an image processing CDN!). Change the dimensions to s220x220 and you’ll see what I mean.

If you run the above command you’ll see that the server returns a 404 “Unsupported Size” error in the headers but the body response is 5xx server error. Assuming the thumbnail size you wanted was a thumbnail size Instagram generated, you can semi-reliably use your custom dimensions, however I couldn’t guarantee that those thumbnail sizes will remain accessible forever. We’ve decided to bite the bullet and use 320×320 image dimensions where we can, so fingers crossed they don’t remove those dimensions!

If you’re crawling the API with a script, you can do something like this in PHP to alter the thumbnail (where $post is your Instagram post object):

We’re working on a little side project here at Humaan, and I thought it would be the perfect opportunity to try out some new-ish frameworks and build tools. For a while now, React and webpack have been all the rage, and I wanted to learn more about them. I’ve previously dabbled in React, but it was a while ago and many things have changed since then.

This article assumes you have some knowledge of JavaScript, the command line, and have Node.js installed on your system. If you have Node.js installed but haven’t used it for a while, I highly recommend updating it to the latest version.

New beginnings

With ECMAScript 6 (aka ES6 or ECMAScript 2015, hereto referred to as ES6 in this article) becoming a thing, I thought I’d also give Babel a try too. For a few months now I’ve wanted to ditch jQuery from my stack, and start writing native JavaScript. The reason for this is that ES6 has a number of new features that means it’s easier to write vanilla JavaScript, and not have to include a ~30 KB jQuery file for each site. jQuery had been a necessity for many years, especially for normalising interaction between different browsers, but as many browsers vendors are (for the most part), following the proper conventions, there’s less need for jQuery nowadays.

If you’re not familiar with webpack, it’s a similar build tool to Grunt or Gulp, but it’s also a module loader like RequireJS. While you can technically use webpack with Grunt/Gulp/etc, I’ve found I haven’t had any need to. webpack can do everything Grunt or Gulp does, and more! webpack is designed with large sites in mind so the idea is to write your JavaScript as a modularised code base so you can re-use and share code, with the goal of making it easier to maintain projects over time.

A significant part of the development stack was set up by following a great article by Jonathan Petitcolas How-to setup Webpack on an ES6 React Application with SASS? There were a few gotchas in the article, and I also wanted to write my React classes in ES6, so while Jonathan’s article was great to get set up with, it left me with a thirst of wanting to find more about ES6 and React.

In this article we’ll set up webpack to handle our CSS, images, and JavaScript. I’ll touch a little bit on React, and we’ll make a basic React app that’ll say “Hello, <name>!” and will update automatically using the very cool hot module loader. Our React app will also be written in ES6 syntax which will be transpiled to ES5 syntax by Babel.

Getting the basics set up

To get started, create a new folder on your computer, and create a package.json file then chuck the following into it:

Next, open up your command-line application of choice, and change your present working directory to the folder you created earlier. We’ve created our list of packages required, so now we need to install them by entering the following command: npm install. Give it a few minutes while all the packages are downloaded and installed to your local filesystem. Once that’s done, create a HTML file called index.html and enter the following:

As you can see, there’s absolutely nothing to the HTML page, except for the script tag referencing a currently non-existent JavaScript file.

Would the real webpack config file please stand up

Now, let’s create our webpack configuration file! In the same folder, create a JavaScript file called webpack.config.js and enter the following:

As there’s a heap of stuff going on in this configuration file, let’s go through it line by line.

entry: getEntrySources(['./src/js/entry.js'])

This line tells the built JavaScript file all the possible entry points into the website, and which files should be loaded accordingly. If you’re going to split your JavaScript files out and only load them on certain pages, this is more important, otherwise loading all JavaScript into one bigger file will be fine.

The output option tells webpack what the name of the compiled JavaScript should be called (and where it should be saved), and you’ll notice it’s the same path as I specified in the HTML. Public path isn’t necessary if you’re loading the file via the filesystem (a la file://), but if you’re serving the site through a web server, chances are this’ll be necessary (in the case of this demo, it’s necessary).

devtool: 'eval'

The devtool option determines how the sourcemap should be generated. Depending on which tool you use to generate sourcemaps, this value can be different, but for us it’s just eval.

Next up is the module option, but as there’s two parts to it, preLoaders and loaders, I’ll do them separately. preLoaders are used on code before it’s transformed, for example, for code hinting tools, or sourcemap tools. loaders are used for modifying the code, and then you can even have postLoaders to handle things like tests over the generated code. For further information regarding loaders and their order, I recommend checking out the loader documentation page.

Using the preLoaders option, we can tell webpack which loaders we want applied to specified files. In our case, I want to generate sourcemaps on the JavaScript files, so we tell webpack that. The test option determines which file(s) to be used, and can be written a number of different ways – as you can see, I’m using RegExp to find all file names ending in .js or .jsx. I’m also excluding the node_modules and bower_components folders as they can be full of hundreds if not thousands of matching files, and I don’t want to include them unless I manually import/require them. Finally, I tell webpack which loader I want to use with the matching files, which is the source-map-loader.

Our first loader can look pretty confusing at first, but it’s pretty simple really: we’re looking for all .scss files nested within the folder “src”. Next up, we have an array of loaders that tell webpack which loaders we want to use, the order of those loaders, and the configuration options to pass on to the libraries themselves. I find that when using a number of loaders, it’s cleaner to use the loaders array, rather than a loader string delimited by exclamation marks.

When specifying loaders using an array, the loader order is from the bottom to the top, so the SCSS files will be compiled with Sass, then Autoprefixer will work its magic, it’ll then be saved as a CSS file, and finally injected into the script with a style tag.

Next, we have options for images included in the JavaScript and CSS. First, we test for image files, then pass them to the image loader which performs optimisations, and then generates URLs for them. You’ll notice the limit query string of 8192. With the limit option enabled, all files under that limit will be base64 encoded and stored in our JavaScript bundle. Any file over that size is left as is and gets linked to via a normal URL. Very clever stuff!

Finally, our last loader is the JavaScript handler which looks for .js or .jsx files in all folders (excluding node_modules and bower_components), then manipulate them with the Babel transpiler and the React hot module loader.

Lastly, at the bottom of the webpack configuration file we have our function that handles environments and adds extra sources depending on which environment we’re in. By default, the environment is ‘development’.

This function enables the webpack development server (DVS) and the hot swap loader to be considered entry-points to the script. If the environment variable NODE_ENV isn’t set to production, then add these sources.

Writing React, ES6 style!

We need to build up our folder structure, so jump back to your terminal prompt and enter the following:

mkdir -p src/{js,css,img}

This will give you the structure:

src/ css/ img/ js/

In src/css, create a file called master.scss and enter the following:

Nothing too special here really, just setting a generic font size and a JPEG image to be a repeating background image. The required JPEG is below:

Now, lets create the entrypoint JavaScript file for the app! Go to src/js and create a file called entry.js and enter what you see below:

First off, we import the CSS into our entrypoint, then we import the class HelloBox from the HelloBox file, along with React. Finally, we render the page using React, and attach it to the body.

If you tried to compile that file, it wouldn’t compile. HelloBox doesn’t exist, so it’s a bust. Let’s resolve that now, create a file called HelloBox.js:

Finally, we’ll create HelloText.js:

Awesome! We’ve written all the code we need to right now.

All the pieces come together

Remember those few scripts that were in package.json? They can act as aliases so you can run common scripts easily without having to remember how to run a certain script each time you go to run it. I defined two scripts, webpack-server, which runs the built-in webpack development server, and web-server which runs a basic Socket.IO web server (so we don’t have to deal with the file:// shortcomings).

My third script is start which is simply a wrapper around the two previous server scripts. By running npm start, it boots up both the webpack-dev-server, and the http-server with the one command. By default, the webpack dev server runs on port 8080, and we tell the HTTP server to run on port 3000. If you open up your browser and load http://localhost:3000 you’ll see:

Hello, Dan!

Sweet! Open up your DevTools window to see more information about how the hot module replacement (HMR) and webpack dev server (WDS) tools are working. You’ll also notice that the image loader found that the above JPEG is less than 8192 bytes in size, so in-lined the image as a base64 encoded image.

One of my favourite parts of webpack is the ability to pass the -p flag via the command line to enable a production-ready build of the output file which will perform optimisations like minification and uglification to your code. In our config we check for a NODE_ENV value of production – to do that, simple prefix NODE_ENV=production to your command line calls, like so: NODE_ENV=production webpack -p. Check out the webpack CLI documentation for more details.

We haven’t yet seen the real power of HMR, so split your screen up so you can see both a code editor, and your browser window (preferably with the console open). Jump into HelloBox.js and change the name from Dan to Joe. Hit save and a moment later the text will change from Hello, Dan! to Hello, Joe! HMR is much more powerful than tools like LiveReload as HMR will reload just the updated component, so if you have forms that have content entered in them, that content won’t be lost (as long as it’s not a child of the updated component).

If you get stuck on one of the code examples, check out the Bitbucket repository below to download the entire example codebase.